Is that really any different than if enterprise clients were demanding support for Firefox 2, Firefox 3, Firefox 4, etc? I've actually been in that situation, a place I worked in 2011 had a web app that only worked properly in Firefox 2.something.
Blame companies for demanding an app specific to one version. Blame the developers for writing apps that only work on one version. Blame Microsoft for making breaking changes between versions. But only one of those things is Microsoft's fault. They've been pushing people hard to update their browser since IE7 was released.
Actually its ensuring that all the show stopping bugs that IE has don't take our app out or make it unusable. Unfortunately clients don't upgrade their browsers if cost is involved.
Blame companies for demanding an app specific to one version. Blame the developers for writing apps that only work on one version. Blame Microsoft for making breaking changes between versions. But only one of those things is Microsoft's fault. They've been pushing people hard to update their browser since IE7 was released.